As is well known in the gas turbine engine technology art, the liner used in the augmentor of a gas turbine engine ensures the structural integrity of the engine case by preventing extremely hot temperatures of the gas path from overheating the outer engine case. Cooling air typically obtained from the compressor or fan flows over the outer surface of the liner wall and flows a portion of the air through a plurality of apertures in the liner to be recaptured into the gas path and discharged through the engine's exhaust nozzle. The liner, obviously must be lightweight and structurally durable. The liner is formed from sheet metal material into a generally cylindrical hollow shell that is co-axially and generally concentric with the augmentor outer case. It is radially spaced from the augmentor case to define an annular passageway where an annular sheath of cooling air flows axially therethrough, while a portion of the cooling air is directed radially into the engine's gas path.
In as much as the liner is considered to be a large diameter structure as is typical in such structures, it responds in complex modes to wide range excitations. Liners that are mounted in cantilevered fashion, as is the case of many existing models, are subjected to a wide range of different loadings and because of the mountings require careful consideration to their design. Added to these considerations is the fact that the liner is corrugated so that it exhibits axial deflections in response to radial loads.
In addition, the liner is formed with a plurality of holes and essentially having a high porosity where there is a wide variety of flow parallel to its axis imposing high dynamic buckling load profiles. Further, service and handling these large diameter structures inevitably results in damage to the leading edge.
It has been observed that the excitation of the leading edge of the liner exhibits a vibratory pattern as shown in FIG. 2. By matching the fundamental radial (RN) and axial (AN) responses with an entrapment means so as to dampen the edge of the structure we have found that we can prevent damage occasioned by vibratory stresses to the leading edge. Additionally, the entrapment structure serves to protect the leading edge from damage occasioned by constant service and mishandling the unit.